Conventional wiring substrates that include a first wiring layer and a second wiring layer that are foamed at the top and bottom, respectively, of an insulating layer to be electrically connected by a via are known. To manufacture such wiring substrates, for example, a dry film is patterned on one side of a base of which both sides are provided with copper foil. The copper foil on the one side is etched, and the dry film is thereafter removed. Thereafter, a through hole is formed in the insulating layer using a laser, and electroplating is performed to foam a via that fills in the through hole and form an electroplating film on the entire surface of the copper foil on the one side. Thereafter, the copper foil on both sides is patterned to complete a wiring substrate (see, for example, Japanese Patent No. 3626486).